1. Field of the Invention
The present invention relates to a vehicle lamp, and more particularly, relates to a vehicle headlight adapted to be equipped in vehicles such as two-wheeled vehicles and some three-wheeled and multi-wheeled vehicles which can lean to one side at the time of turning around, i.e., going around a curve, moving circularly, or the like.
2. Description of the Related Art
FIG. 1 shows a projection-type headlight 90 as an exemplified configuration of a conventional headlight. The headlight 90 includes a light source 91, an ellipse group reflecting surface 92 such as a rotated elliptic surface having a first focus f1 located at the light source 91, a shutter 93 arranged in the vicinity of a second focus f2 of the reflecting surface 92, and a projection lens 94.
The shutter 93 is provided in luminous flux, which is in a generally circular shape in its cross section and converges from the reflecting surface 92 to the second focus f2. The shutter 93 is able to block a lower half part of the luminous flux in section to obtain the reflecting light in the shape of a generally upper chord semicircle in section. The luminous flux traveling from the reflecting surface 92 is flipped vertically and horizontally after converging to the second focus f2, so that the semicircular upper chord part of the reflecting light can be projected as a semicircular lower chord part thereof through the projection lens 94 in the illumination direction. Consequently, the light illuminated from the headlight 90 does not include light rays traveling upward, resulting in a xe2x80x9cpassing-by modexe2x80x9d light distribution pattern (i.e., a low beam) S which is substantially rectangular, and long in a horizontal direction as shown in FIG. 2.
A two-wheeled vehicle leans to the left side at the time of going around a left curve. As shown in FIG. 3, the low beam distribution pattern S leans to the left downside with respect to a horizontal axis H on a screen because the headlight 90 is fixed on the vehicle body. In other words, there is a problem in which the headlight cannot sufficiently illuminate the left forward area ahead of the vehicle in the traveling direction. Similarly, such a problem may be caused in a three-wheeled vehicle, multi-wheeled vehicles or in vehicles in which a driver""s seat leans to one side at the time of going around a curve.
For solving at least the above problems, there is proposed a method for always preventing the low beam distribution pattern S from being leaned to one side with respect to the surface of earth by having an entire set of the headlight 90 turned around its center axis. However, the turning movement of the two-wheeled vehicle varies depending on its driving conditions. For example, when the two-wheeled vehicle runs at a comparatively high speed, it is able to turn around as the vehicle body leans to one side without substantially using a handle bar. On the other hand, when it runs at a low speed, the handle bar must be used for steering to the desired side to turn around. In the great majority of actual driving cases, the vehicle turns while running at a high speed. Therefore, the turning of headlight in synchronization with the handle operation is not necessarily required for satisfying all of the conditions for the turning of the vehicle. In fact, it cannot be a complete measure to improve the problem.
For solving the above problems, one aspect of the present invention is to provide a vehicle lamp capable of obtaining a desired light distribution pattern in a desired direction for a two-wheel vehicle, multi-wheeled vehicle, or a vehicle having a vehicle body which leans to one side at the time of turning. In addition, another aspect of the present invention is to provide a vehicle lamp capable of keeping a horizontal line or curve of the desired light distribution pattern substantially parallel or in a set position relative to the surface of earth or other driving surface.
According to an embodiment of the present invention, as concrete means for solving the above problems, a vehicle lamp mounted on a vehicle body can have the following features. That is, the vehicle lamp can include: a light source; a projection lens; a first ellipse group reflecting surface having a movable part provided at at least one portion thereof, the first ellipse group reflecting surface having a first focus located approximately at a position of the light source, the first ellipse group reflecting surface being configured such that light rays traveling from the first ellipse group reflecting surface is adjusted to enter in the projection lens, said movable part preferably having at least one opening part; a second ellipse group reflecting surface corresponding to an area covering a moving range of the opening part formed or installed in the movable part of the first ellipse group reflecting surface, said second ellipse group reflecting surface having a first focus located approximately at the light source, the second ellipse group reflecting surface being configured such that light rays traveling from the second ellipse group reflecting surface are adjusted to enter in the projection lens; a drive unit connected with the movable part of the first ellipse group reflecting surface; and a fixing member arranged such that the movable part of the first ellipse group reflecting surface is interposed between the fixing member and the second ellipse group reflecting surface, the fixing member retaining the movable part of the first ellipse group reflecting surface in place.
In this constitution, a shape of light distribution formed by light rays from the projection lens can be substantially rectangular having a long side extending in a horizontal direction, and the movable part of the first ellipse group reflecting surface turns by actuating the drive unit such that the long side of the shape of the light distribution is kept in a substantially horizontal position with respect to a surface of earth or in a position that facilitates illumination in the turning direction. Furthermore, light rays that pass through the opening part of the first ellipse group reflecting surface can reflect from at least a part of the second ellipse group reflecting surface, and then converge to a point in a predetermined direction to illuminate an area ahead of the vehicle body.
Conventionally, as described above, the vehicle headlight leans to one side when the vehicle turns about, so that a light distribution pattern also leans to the same side. The present invention can solve this and other problems by providing, as shown in one embodiment of the invention, a vehicle headlight in which a generally rectangular light distribution pattern can be substantially parallel with the surface of earth (i.e., the surface of road) by turning the movable part. In addition, a shutter part can be integrally provided which works together with the movable part, so that a desired light distribution pattern in a desired direction is obtained. Furthermore, using the relative movements of an opening of the first ellipse group reflecting surface and the position of the second ellipse group reflecting surface, the luminous flux can be biased in the tuning direction for further improving visibility. Therefore, this embodiment of the vehicle headlight produces an excellent effect on performance improvement of the vehicle lamp.
An embodiment of the vehicle headlight according to the present invention can include a shutter part which is capable of working together with the movable part of the first ellipse group reflecting surface. In this constitution, it is preferred that the movable part of the first ellipse group reflecting surface turn around by actuating the drive unit such that an upper end of the shutter part is kept in a horizontal position with respect to the surface of earth.
In a vehicle headlight according to the invention, it is preferred (but not necessary) that the movable part and the shutter part of the first ellipse group reflecting surface be integrally formed. The light rays that pass through the opening part and reflect on the second ellipse group reflecting surface can illuminate a forward area in a traveling direction when the vehicle body leans to one side. A second focus of the second ellipse group reflecting surface may preferably be located in the vicinity of a focus of the projection lens. It is also preferable for the first ellipse group reflecting surface to have a fixing part, and a portion of the second ellipse group reflecting surface for covering the opening part may be connected with the fixing part of the first ellipse group reflecting surface through a stepped portion. The first ellipse group reflecting surface may have a fixing part behind the movable part, and it is preferable that the fixing part and the movable part of the first ellipse group reflecting surface can function as a continuous surface.
In a vehicle headlight according to the invention, the first ellipse group reflecting surface may be preferably located inside the second ellipse group reflecting surface. Turning of the first ellipse group reflecting surface can be performed by the drive unit based on an output of a sensor for detecting inclination of the vehicle body, an output of a sensor for detecting a running speed of the vehicle body, or an output of a sensor for detecting a steering angle of a steering wheel or a handle bar. It is preferred that the drive unit include a motor and a gear mechanism, but can also include a magnetic, fluid, gravity or other type of drive unit as well.